Dose limit examples
Transcripción
Dose limit examples
• • Resumen de unidades Activity is the transformation (disintegration) rate of a radioactive substance – Curie (Ci) – Becquerel (Bq) - S.I. Unit 1 Bq = 1 disintegration per second (dps) 1 Ci = 3.7 x 1010 dps = 3.7 x 1010 Bq Absorbed dose is a physical quantity which represents the energy imparted by radiation onto an absorbing material. – Rad = 100 ergios / 1g – Gray (Gy) - SI Unit 1 Gy = 1 joule per kilogram 1 Gy = 100 rads • Dose Equivalent (DE) may be regarded as an expression of dose in terms of its biological effect. DE takes account of the fact that, for a given absorbed dose, such as 1 Gray, a radiation of one type and/or energy may give rise to a greater biological effect than a radiation of another type and/or energy. – – • DE = Absorbed Dose x Quality Factor (Q) , Q depends on the type of radiation. Q = 1 for gamma, x-ray and beta Q = 10 for alpha – Q is used to compare the biological damage producing potential of various types of radiation, given equal absorbed doses. The effectiveness of radiation in producing damage is related to the energy loss of the radiation per unit path length. The term used to express this is Linear Energy transfer (LET). Generally, the greater the LET in tissue, the more effective the radiation is in producing damage. rem (Roentgen Equivalent Man) – SIEVERT (Sv) - S.I. Unit 1 Sv = 100 rems Exposure is a quantity that expresses the ability of radiation to ionize air and thereby create electric charges which can be collected and measured – Roentgen (R) 1 R = 2.58 x 10-4 C/kg of air – 1 R = 0.01 Sv Symptoms frameworks • Symptoms of acute radiation (dose received within one day): – – – – – – • Dose examples – – – – – – – – • 0 – 0.25 Sv (0 – 250 mSv): None 0.25 – 1 Sv (250 – 1000 mSv): Some people feel nausea and loss of appetite; bone marrow, lymph nodes, spleen damaged. 1 – 3 Sv (1000 – 3000 mSv): Mild to severe nausea, loss of appetite, infection; more severe bone marrow, lymph node, spleen damage; recovery probable, not assured. 3 – 6 Sv (3000 – 6000 mSv): Severe nausea, loss of appetite; hemorrhaging, infection, diarrhea, peeling of skin, sterility; death if untreated. 6 – 10 Sv (6000 – 10000 mSv): Above symptoms plus central nervous system impairment; death expected. Above 10 Sv (10000 mSv): Incapacitation and death. Dental radiography: 0.005 mSv Mammogram — Single Exposure, Equipment Mean: 2 mSv Mammogram — Procedural Mean, Equipment Variation: 4 mSv - 5 mSv Brain CT scan: 0.8–5 mSv Chest CT scan: 6–18 mSv Gastrointestinal series X-ray investigation: 14 mSv International Commission on Radiological Protection recommended limit for volunteers averting major nuclear escalation: 500 mSv International Commission on Radiological Protection recommended limit for volunteers rescuing lives or preventing serious injuries: 1000 mSv[10] Hourly dose examples – – Average individual background radiation dose: 0.23μSv/h (0.00023mSv/h); 0.17μSv/h for Australians, 0.34μSv/h for Americans Highest reported level during Fukushima accident: 1000 mSv/h reported as the level at a pool of water in the turbine room of reactor two. • Yearly dose examples – – – – – – – – – – – – – – – – • Maximum acceptable dose for the public from any man made facility: 1 mSv/year Dose from living near a nuclear power station: 0.0001–0.01 mSv/year Dose from living near a coal-fired power station: 0.0003 mSv/year Dose from sleeping next to a human for 8 hours every night: 0.02 mSv/yr Dose from cosmic radiation (from sky) at sea level: 0.24 mSv/year Dose from terrestrial radiation (from ground): 0.28 mSv/year Dose from natural radiation in the human body: 0.40 mSv/year Dose from standing in front of the granite of the United States Capitol building: 0.85 mSv/year Average individual background radiation dose: 2 mSv/year; 1.5 mSv/year for Australians, 3.0 mSv/year for Americans Dose from atmospheric sources (mostly radon): 2 mSv/year Total average radiation dose for Americans: 6.2 mSv/year New York-Tokyo flights for airline crew: 9 mSv/year Dose from smoking 30 cigarettes a day: 13-60 mSv/year Current average dose limit for nuclear workers: 20 mSv/year Dose from background radiation in parts of Iran, India and Europe: 50 mSv/year Dose limit applied to workers during Fukushima emergency: 250 mSv/year Dose limit examples – – – – Criterion for relocation after Chernobyl disaster: 350 mSv/lifetime In most countries the current maximum permissible dose to radiation workers is 20 mSv per year averaged over five years, with a maximum of 50 mSv in any one year. This is over and above background exposure, and excludes medical exposure. The value originates from the International Commission on Radiological Protection (ICRP), and is coupled with the requirement to keep exposure as low as reasonably achievable (ALARA) – taking into account social and economic factors. Public dose limits for exposure from uranium mining or nuclear plants are usually set at 1 mSv/yr above background. RADIACTIVIDAD NATURAL Radiactividad Natural en la Comida 40K 226Ra pCi/kg pCi/kg Plátano 3,520 Nueces 5,600 Zanahorias 3,400 1 1,0007,000 0.6-2 Patatas 3,400 1-2.5 Cerveza 390 --- Carne Roja 3,000 0.5 Limón 4,640 2-5 --- 0-0.17 Comida La radiación interna proviene de las sustancias radiactivas presentes en los alimentos, en el agua y en el aire, las cuales, al ser ingeridas o inhaladas, se absorben en los tejidos vivos. Los principales isótopos radiactivos que contiene el cuerpo humano son el potasio-40, el carbono-14 y el tritio NOTA: 1Ci = 1 Curio = 3.7x1010 Bq 1 Bq = 1 Becquerel = 1 desintegración / s Agua del Grifo RADIACTIVIDAD NATURAL El Radón es una de las principales sustancias que contribuye a la dosis que recibimos de manera natural. El Radón es un gas noble que se filtra hasta el interior de nuestras casas desde el subsuelo. Es curioso observar cómo ésta dosis es mayor en países fríos, donde ventilar la casa puede costar algún catarro Rayos Cósmicos Gamma (Fuera) Gamma (Dentro) Australia UK Suiza Suecia España Portugal Noruega Holanda Luxemburgo Italia Irlanda Grecia Alemania Francia Finlandia Dinamarca Bélgica Austria DOSIS MEDIA ANUAL PROVENIENTE DE RADIACIÓN NATURAL Radón TIPOS DE RADIACIONES IONIZANTES :::::::::::::: ALFA Detenida por una hoja de papel y llega solamente hasta unos cuantos centímetros. ::::::::::::::::::::::: BETA Detenida por aluminio o algunos metros de aire ))))))))))))))) GAMMA Y RAYOS X ))))))))))))))))))))))) NEUTRONES Detenida por blindaje de plomo o concreto Detenida por Hidrógeno o Boro Ejemplos de efectos radiación • Estocasticos – Cáncer – Malformaciones y enfermedades hereditarias – Tumores malignos – Leucemias • Deterministas – – – – – – – – – – – Cataratas oculares Eritema Cáncer cutáneo Alteraciones hematológicas Aplasia medular Anemias Caída del cabello Inflamación bronquial Fibrosis pulmonar Neumonitis Esterilidad CUADRO HIPER-AGUDO (EFECTOS INMEDIATOS en minutos) SÍNDROME DE IRRADIACIÓN: Diarreas, Fiebres, Náuseas,Vómitos Infecciones, Quemaduras con descamación seca o húmeda Hemorragias intestinales TÉCNICAS DE PROTECCIÓN RADIOLÓGICA TIEMPO DISTANCIA BLINDAJE d